One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 8 e) l' C6 A6 E; H+ E
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
/ d9 Z: H! H$ Q0 d/ T( e5.39.217.77active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
1 v# O; q2 o$ ~8 A" m7 l' T$ M1 p5.39.217.77Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
/ M' u' a! |+ p: O* ]erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。. [; N6 v3 `. {' A/ A, _
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. 公仔箱論壇- i7 a" W' m) C2 g# _
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.
$ d# p$ m0 @8 }6 q' p; I: k0 J; }TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。* f6 Q8 D3 [& Z2 d3 C2 P

' [# t* z& b9 _tvb now,tvbnow,bttvb
) M: t* _. e$ O% |7 `$ RTVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
+ H' O9 a; S' ?TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas# K' B" l( E) \/ d- V$ E
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
' M9 Y% c* Q7 H+ ~' r8 O9 e) Fplume reached as high as 50,000 feet.TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。9 i9 O. ~/ E" @. I8 c
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8 U+ R; l1 z5 B" Y7 e公仔箱論壇Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
* [3 w( r* A- q/ x3 b. e7 Ntvb now,tvbnow,bttvbsatellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
/ w- X, Q& B3 ?9 zyears. The island’s jagged edges were created by massive avalanches.TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。1 E% c1 h6 O" V; h7 K' S
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Augustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring
6 z3 Q6 D+ `% B; g( n) Qof Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
+ S# ?+ a& Q' E" E+ @1 l$ F- R" btvb now,tvbnow,bttvbocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
$ }5 z" {. y6 R. s5 q0 B0 V) _TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。the continental crust, creating magma that drives the volcanic eruptions
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, C3 ~, ~1 B6 W& i V T# h% ^. e! bTVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。 公仔箱論壇( ~' i& _, E3 o8 _1 e& _" k
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Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
/ x5 [ I' o7 n3 Y- f% tTVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.tvb now,tvbnow,bttvb) s& z5 D( a# t) A' \) q
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The smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising # i9 [. e! B1 s/ f* I8 j
and cooling of the air above. In contrast, a dark gray cloud of ash near the ground is probably an avalanche of hot ash and rock known 5.39.217.77- h( F: \( p K
as a pyroclastic flow.
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This photo sparked a debate among scientists about what caused the hole in the clouds above the eruption. Three possible options came up:
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* Q* I6 X: C& A! } * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.
$ [9 J1 ^4 D/ j; }0 D) f9 X5.39.217.77 * A shockwave from the eruption could have blown a hole in the cloud deck.
( `$ ]3 T. k# r5 a. [6 } p1 D公仔箱論壇 * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.0 K$ W' X5 B/ ~0 Y0 C4 S7 y/ f
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Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。" ]) ]( W0 m% |- d6 K" v6 A
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 whentvb now,tvbnow,bttvb9 Z4 |, z9 A: e1 i
the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.. O( G) K) l* D$ `8 R9 u' u/ h
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Redoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.* ~+ k1 g* R) \- L4 \
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8 u j6 i3 l* C+ b3 xMount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in
9 ?/ s2 y6 U1 ?5 v5 {; m/ H. TTVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。 the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one 5.39.217.77( m! @( U- b# f$ w
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
8 h" ^7 B* ]) g) t6 n5 k! Ethis picture are from forest fires ignited by lava.5.39.217.775 _5 p* z4 G; Q+ K- U7 j$ C
! y% y% }9 ~0 A" c9 o- Btvb now,tvbnow,bttvbEtna is a stratovolcano located on the island of Sicily. It is one of the most studied volcanoes in the world and. at 500,000 years old, it may
7 n% d% Y6 ~$ P; N; O" w3 ~公仔箱論壇also be the oldest-known active volcano.# I) U2 ^* ?9 v4 M: Z* \* d6 \
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A NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。1 H! ]: O, `& R/ q' T; z4 t- G
and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.
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Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。3 m1 k8 F& @% D
The second highest peak in Mexico at 17,800 feet, this glacier-covered stratovolcano has erupted at least 20 times in the last 500 years and has caused
5 W8 k, n$ A) D5.39.217.77multiple evacuations of the city. This eruption in 2001 was caught by astronauts on the International Space Station, near the end of a seven-year period
3 N1 {3 M9 i! I* ?' G. Vof frequent activity. The plume reached heights of around 30,000 feet.
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3 ]! b- u) |4 L8 |6 s" q5 l8 zTVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。
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This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the 5.39.217.77* t# i3 y% w1 j( x/ z
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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" U) f, T! Q3 Z1 F; C0 U5.39.217.77Chaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic 公仔箱論壇8 w( z8 L, H, f; h3 T& G/ r
flows and volcanic mudflows called lahars. The caldera is relatively small at less than two miles wide, and sits on the flank of the larger Michinmahuida volcano.
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This image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra 公仔箱論壇& L( X. z9 [' ^0 B! x
is a shield volcano, which are made mostly of previous lava flows and tend to be broad and gently sloping. The Galapagos are part of an island chain " D3 D% `1 R. q
formed by a hot spot where a plume of hot mantle rises up and melts the base of the ocean crust. As the Pacific plate moves over the relatively
5 D/ x0 i9 l8 W/ |: y6 O公仔箱論壇stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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NASA’s Terra satellite snapped this image of Shiveluch volcano erupting on Russia’s Kamchatka peninsula at the edge of the Pacific Ring of Fire in 2004. * B6 O2 i" E, k9 v$ m1 o7 g
A lava dome had been growing in the volcano’s crater, followed by intermittent eruptions that lasted weeks. Shiveluch is a 10,400-foot-high stratovolcano
' Y# _! I0 T5 |- i$ P; xTVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。that is at least 60,000 years old and has been erupting fairly often for the past 10 years. Its dome has collapsed multiple times, most recently in 1964,
4 Y1 c" u" v' i9 G V1 f% q公仔箱論壇causing avalanches of debris into the crater. |